Abstract

Details and results are presented of aerial radiometric measurements undertaken in summer 1988 over an area of restricted livestock movement in West Cumbria. The project was planned in June and July on the basis of discussions between MAFF and SURRC. The prototype aerial spectrometer developed at SURRC in March was used in a helicopter for three purposes. Firstly the sensitivity and spatial resolution attainable over variable and, in some places mountainous, terrain was confirmed, supporting the conclusions of earlier flight trials in Scotland. Secondly it was confirmed that 134Cs could be detected semi-quantitatively within the survey area, providing insight into the origins of anthropogenic deposition of 137Cs. Finally the distribution of both natural and anthropogenic gamma ray emitting radioactivity was determined within the survey zone.
The survey was conducted successfully in between 22nd August and 3rd September 1988. Despite unseasonably poor weather more than 1800 measurements were recorded from an area of over 45000 hectares. The detector performance and sensitivity was as expected, and it has been possible both to detect 134Cs and to produce high resolution maps of the radioactivity within this area. A comparison of the results of other analyses of environmental materials from parts of the survey area, including a programme undertaken by MAFF in 1988, and the aerial results confirms the overall validity of the calibration method used.
Both 134Cs and 137Cs maps show considerable spatial variation throughout the survey zone and can be used to identify the areas of peak deposition due to Chernobyl. This basic information may be of use for devising and evaluating agronomic strategies to minimise the transfer of artificial nuclides through the food chain, and to help alleviate the problems experienced by farmers working in the restricted areas since the Chernobyl accident. The prototype detector and method used both show considerable potential for further development.

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